Control system



March 29, 1938. A, Pm, 2,112,251

CONTROL SYSTEM Filed Sept. .30, 1935 4 Sheets-Sheet l March 29, 12938.,

A. PFAU CONTROL SYSTEM Filed Sept. 50. 1935 4 Sheets-Sheet 2 i g /09 92 i g Y 1 l l K g\\\\\w\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ March 29, 1938. A, PFAU 2,112,251

CONTROL SYSTEM Filed Sept. 30, 1955 4 Sheets-Sheet 3 Patented Mar. 29, 1938 PATENT OFFICE CONTROL SYSTEM Arnold Pfau, Milwaukee, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwau kee, Wis, a corporation of Delaware Application September 30, 1935, Serial No. 42,834

17 Claims.

This invention relates to improvements in control systems for prime movers and particularly to constructions and systems for operating a plurality of prime movers. from a single means re- 5 sponsive to the speed of such prime movers.

Systems in which large amounts of power are produced generally require a plurality of prime mover units or at least, consist of a number of units to which additions of other units are made 10 from time to time. In all power systems it is desirable that the speed of all of the units, or the so-called system speed, be kept approximately constant or that such variations of speed as occur be'kept within predetermined limits.

l5 Due to the increasing magnitude of such power systems, the magnitude of load variations occurring therein is becoming a decreasingly small percentage of the total load and such load changes as do take place normally are small and gradual variations, rather than large and sudden changes. Is is therefore no longer necessary that all of the plurality of prime movers in a large system be responsive to all of the load variations and such practice is even undesirable because it contributes both to difliculties in operating the system and to system instability. It is, however, desired that means be provided by which a sufiicient number of such units may be controlled, within their most eflicient limits of operation, as will be adequate to maintain the power values in the system at the desired point regardless of load variations on the system. Such controlmeans preferably employ only a single highly sensitive speed responsive device for 35 controlling all of the units which need to be controlled. The control means operated by such speed responsive device must then be of such character as to .avoid the use of the speed responsive device as a source of power for control 40 purposes and the control must be responsive even tothe slightest variation in system speed. Each of the control means must be immediately responsive to any variation, however slight, in the system speed and must also be operable individually to allow normal-operation of each unit alone or in parallel with other units, and must be provided with means to meet abnormalities or emergencies arising in operation of any one of the units without disturbance of operation of .79 any of the other units controlled by the same speed responsive device.

It is therefore among the objects of the present invention to provide a control system for prime movers in which a single speed responsive device provides only the control impulses necgzs essary to actuate the individual regulating devices of a plurality of units.

Another object of the invention is to provide a control system for a plurality of prime movers connected into a single system in which each of v 5 a plurality of commonly controlled prime movers is provided with individual means controlling regulation of each unit within the maximum and the minimum load limits determined to be most effective for each one of the units.

Another object of the invention is to provide a control system for a plurality of prime movers connected into a single system in which each of a plurality of units is controlled in common by a single speed responsive device and which may 1 be voluntarily adjusted or continuously controlled without disturbing operation of the portions of the control system common to all of the units.

Another object of the invention is to provide a control system for a plurality of prime movers controlled in common and connected into a single system in which emergency condition responsive devices applied to each unit may operate to supersede the common control of any unit affected without aflecting the control of other units by the common regulating system.

Another object of the invention is to provide a control system for a plurality of prime movers connected into a single system in which a speed responsive device controls energization of the several control means for periods of time which are variable dependent on the amount of speed change in the system.

Objects and advantages other than those above set forth will be apparent'from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of the present invention illustrating particularly the electric circuits and so much of the mechanical 40 construction as is necessary to a complete comprehension of the operation of a system embodying the invention;

Fig. 2 is a vertical sectional view, taken on an axial plane, of a speed responsive device herein termed the master controller which controls or governs a plurality of other means by which the speed of any machines to which such means are applied, may be controlled;

Fig. 3 is an end view, looking in the direction 5 of the arrows in Fig. 2, of the master controller with parts thereof, which are already illustrated in Fig. 2, omitted for the sake of clearness in disclosure;

Fig. 4 is a vertical cross sectional view of the master controller taken on the plane IV--IV of Fig. 2;

Fig. 5 is a vertical sectional view taken on an axial plane through means for individually controlling a machine and which means in itself is controlled by the master controller;

Fig. 6 is a sectional view on plane VIVI of Fig. 5, looking in the direction of the arrows, and illustrating the operating means for such control valve;

Fig. 7 is a partial rear elevation of Fig. 6, to illustrate the arrangement of the means for operating the control valve shown in Fig. 5;

Fig. 8 is a vertical sectional view similar to that shown in Fig. 5 but illustrating a modified form of means for operating the control valve of a machine to be regulated;

Fig. 9 is a diagram illustrating the operation of the master controller and showing the operation of the contacts thereof plotted on axes of contact stroke and time; and

Fig. 10 illustrates the variation in load obtainable with a predetermined setting of load limit devices to secure operation of any of the units within its most efllcient range.

Referring more particularly to the drawings by characters of reference, reference numerals l6. and I! designate prime movers herein shown as hydraulic turbines, which prime movers may,

however, be of any character operable by a fluid of which the flow is controlled to vary the operation of such prime movers. The hydraulic turbines shown are illustrated as being of the type to which water is supplied by penstocks (not shown) through a spiral casing under the control of one of the usual types of gates which are also not shown. The prime movers l6 and ll are shown as severally driving energy translating devices I3 and I 9, herein shown as electric current generators which are severally connected with an electric power transmission line 2|. Connection of the several prime mover generating units to line 2! in parallel with other units is individually controlled by circuit breakers 22 and 23 and connection of all adjacent units to other groups of units in the system is controlled by a circuit or from any other suitable source. The flow of fluid pressure to the servomotors is severally controlled by valves 28 and 29. The valves are controlled by the cooperation of a plurality of electric motors ll, 32 and 33 acting on the valve 28. and a plurality of electric motors", 31 and 38 acting on the valve 29, and also by solenoids ll and I2 acting directly on the servomotors 2i and 21 respectively. The several connections of the ti and 42 with sources of electric energy such as a battery 63 are controlled by circuit breakers l3 and 44, respectively, which are the description of the construction of the servomotors and the valves.

Movement of the valves 28 and 29 may be remotely indicated by insertion and withdrawal of portions of resistances 46, 41, 4t and 49 from the several circuits controlling indicating instruments SI, 52, 53 and 54, respectively, to indicate the movement of such valves. The motors 3| and 33 are controlled by the operation 01 double pole switches 56 and 51 and motors 36 and 38 are controlled by operation of double pole switches 58 and IS. A plurality of relays 6i and 62 are interconnected with motors 32 and 31 and control the operation of such motors, except as explained immediately below, while energization of the relays is controlled. by speed responsive means which will be hereinafter designated as the master controller and which will be described in detail. The motors 32 and 31 are severally controllable by switches 63 and 64, respectively, by which the motors may be energized individually for rotation in either direction regardless of whether or not the master controller is in operation and whether or not the relays SI and 62 are energized through switch 6 from the so-called house or auxiliary line 61 which is energized from the battery 63. The several motors, indieating instruments, relays and solenoids are energized from the house line Bl-an'd are connected and disconnected by the joint action of back contacts on the circuit breaker 24 and by operation of the manually operable switch 8. The master controller, of come, cooperates with the several double pole switches and the relays to control energization of all of the valve operating motors.

The detailed construction of the device herein termed the master controller may be best understood by reference to Figs. 2, 3 and 4 in which a base plate II has mounted thereon a motor 12 which is of the synchronous and preferably of the high speed type. The motor is connected with the power line 2| and accordingly is responsive to changes in the electrical values in such line which are responsive to the speed of the prime mover generating units connected therewith. The shaft of motor 12 is coupled with a spindle It by a coupling 14 which is preferably of such character as to permit some axlalmovement oi the motor 12 without allowing such movement of the spindle l3 and as to prevent delay in transmission oi torque between the shafts. The spindle I8 is suitably supported in a frame It which also provides support for other portions of the controller structm'e to be described. The spindle has mmmted thereon arms or plates 11 formingayokeonwhlcharemountedbellcranks 13 and II which carry weights 8i and 82 connected by a spring 33. The weights, bell cranks and spring form a speed responsive means of the character known as a flyball governor. The several cranks of such governorare severally connectedthrough links It and 81 with a sleeve." which is axially movable on a stationary-sleeve ll enclosing the spindle 13. D n outward movement oi the flyban weights under the action of centrifugal force due to rotation thereof by the motor 12. Contacting surfaces of axialLv moving sleeve 38 and stationary sleeve 90 thus move spirally relative to each other, which minimizes force required to secure movement between such surfaces.- A lever 80 is pivotally mounted on the sleeve 83 for movement thereby and is pivotally connected, at one end thereof, with a nut 9| movable on a threaded spindle 92 and forming a fu crum for such lever. The position of nut 9I may be varied as desired by rotation of spindle 92 by a hand wheel 93 which is retained in any position into which it is turned, by a locking device 94. The free end of the lever 89 is connected to one conductor of the auxiliary house line 61 and is provided with a contact 96 which may engage with either of two contacts 98 and 99, movably mounted on opposite sides of the contact 96. The contacts 99 and 99 are connected with and control the circuits of the coils of the relays 6i and 62 and are mounted on springs IN and I92 in insulated relation in a yoke I93, which is supported from a rod I94, reciprocally mounted in frame 16. Rod I94 is connected by a link to a lever I96, mounted on frame 16, with a crank mechanism I01 adjustably connected with a worm wheel I98 also mounted on frame 16 and engaging with a worm I99 mounted on the master controller spindle 13. The whole of the master controller excepting motor 12, coupling 14 and adjusting hand wheel 13 with lock 94, is enclosed within a casing III.

The hand adjusting wheel 93 may also be controlled automatically to vary the basic speed at which the master controller operates in response to some condition affecting the operation of the units such as the head or tail water level or such basic speed may be changed according to a predetermined program. Thus, the mechanism designated by reference numerals 12 to 19 inclusive of U. S. Letters Patent No. 1,922,323, issued to Arnold Pfau on August 15, 1933, may be applied to spindle 92 in place of hand wheel 93 to adjust the master controller contact lever 89 dependent on head or tail water level.

It will-be apparent to one skilled in the art that other automatic means known to the art may also be applied to the master controller to vary the operation thereof as desired.

The master controller thereiore provides means responsive to variations in the frequency of the power line 2I and hence in the speed of the prime mover generating unit for closing and interrupting circuits controlling the operation of the motors 32 and 31, which adjust the position of the valves 28 and 29. Such means comprises the motor 12 and the flyball governor which controls engagement of the contacts 98, 99 and 99 by which the circuits of the valve adjusting motors are controlled. The moment at which contact 96 units, that is, the frequency of the generator output, is indicated by a pointer II2 movable over a suitable scale formed on the outside of the master controller housing III. The pointer is mounted on a' shaft II3 which is connected by links H4 and H6 with sleeve 89 so that axial movement of the sleeve causes rotation of the shaft I I3 and of pointer H2 over its scale. A second pointer I I5 is connected with the nut 9I movable on spindle 92 and moves over a suitable scale on the master controller housing to indicate what changes have been made in the setting of contact 96.

It will be understood that the servomotors and the valves controlling such servomotors are identical for each of the units controlled, and that such units may be multiplied indefinitely. It is therefore necessary only to describe the structure of the servomotor 26 together with its control valve 29 as illustrated in Figs. 5, 6 and '1. The

servomotor 26 comprises a cylinder I2I and a piston I22 reciprocating within the cylinder whenfluid pressure is admitted to the cylinder through the valve 29 which is a type of slide valve reciprocating within a valve casing I23 to which fluid pressure is admitted by way of a port I24 and from which the pressure is discharged by way of a port I26. A stem I21 extends through one end of the valve casing and is movable into engagement with the valve as will be explained. The valve 29 is formed with a stem I29 extending through the end of the valve casing. Stem I21 is provided with an enlargement I29 of magnetic material formed thereon to cooperate with a coil I3I formed around such enlargement, the two portions together forming the solenoid generally designated at H in Fig. 1. Such solenoid core I29 is biased into one position by the action of .an adiustably mounted spring I32 to secure opening operation of the valve upon deenergization of coil I3I as will appear hereinafter. Valve stem I28 is formed with a loop I33 intermediate its ends and is connected at its outer end with a bell crank I34 which has its pivoting point on a bracket I36 extending from the valve casing I23. One end of the bell crank I34 has attached thereto a rod I31 guided in the bosses I35 of bracket I36. The rod l31 has formed thereon a cam-I38 movable within the valve stem loop I33 to form a rate of movement limiting device of the character disclosed in U. S. Letters Patent No. 1,839,257, issued to Arnold Piau on January 5, 1932. The other end of the bell crank I34 is connected by way of a link with an arm I4I mounted on the rod of servomotor piston I22. The arm I is also attached to a floating lever I42 having a point intermediate its ends resiliently connected with the bell crank I34 by a rod I43 movably connected with the lever I42 and operating against the action of springs I46 and I41. The other end of the floating lever I 42 is connected with a screw threaded rod I49 which extends into a casing I49 and through a sleeve II centrally located within the casing. Externally threaded sleeves I52 and I63 are mounted in and extend from the ends of the casing and are arranged over the sleeve I5I. The ends of the sleeves I52 and I53 are substantially closed by internally threaded caps I56 and I51 respectively, which move longitudinally as the sleeves I52 and I53 are rotated. Such movements of the caps I56 and I51 are guided respectively by rods I69 and I59 extending from the casing I49 and the caps carry contact members I6I and I62 respectively to engage with and vary the amount of resistances 49 and 41 n circuit with the indicating instruments 5| and 52. A worm wheel I63 is secured on or formed as a part of the innersleeve I5I and worm wheels I64' and I65 are likewise mounted on or formed as portions of sleeves I52 and I53respectively. The worm wheels severally engage worms I61, I69 and I69 which are supported in and extend through the valve drive casing I49. Such worms are respectively connected with the spindles of motors 3|, 32 and 33 by means of suitable slip or overrunning clutches as indicated at Hi. The

movement of rod I48 by motor 32 is limited by the position of collars I13 and I14 and the movement of such rod by motors 3I and 33 is'also limited by the position of collars I16 and I11. The individual functions of the several portions of the structure described will be'apparent from the explanation of the operation 'of the system hereinafter.

A modified structure of the control valve and I99 and I91.

of the drive heretofore described, is shown in Fig. 8 which differs from the structure shown in Figs. 5, 6 and 7 inthat the single solenoid I29, I9I is now replaced by a plurality of solenoids comprising the cores I9I and I92 associated respectively with coils I99 and I94 to form a double solenoid acting against a spring I99 and 'replacing the motor 32 of the embodiment previously described. The functions of motor 32 in operating the valve shown in Figs. 5, 6 and 7 are now performed by the double solenoid. The one end of floating lever I42 is now no longer connected with the arm I on the rod of the servomotor piston I22, but is connected directly with the valve stem I28 through a resilient connection comprising a spring I 91 mounted on the stem I29 and arranged within a spring casing I99 mounted on the end of the lever I42. Bell crank I94 and the center portion of floating lever I 42 are now connected directly by a link I99. The mechanism for reciprocating rod I49 by means of motors 9i and 99 is also somewhat modified from that previously shown in that sleeve I5I is now replaced by two sleeves, I99 and I91, and that collars I19 and I14 are replaced by a single collar I99 mounted on rod I49 between the sleeves The sleeves I52 and I99 remain substantially as previously shown and the drives of the-motor 3i and the motor 99 likewise remain the same.

The operation of the master controller and of the several control valves can be best understood by considering the several conditions under which the system must operate. As shown, the mtem is presumed to be in operation at normal speed and hence the several prime mover generating units are presumed to be delivering current at the frequency of the on line 2i over the circuit breakers 22 and 29. Circuit breaker 24 is closed and is kept in the closed position. To simplify explanation of the operation of the system, the operation of one unit will be described, the operation of other units being similar thereto. Operating fluid is then being supplied to the prime mover I9 and the gate or valve therein is in a predetermined position in which it is retained by the balanced pressure on opposite sides of the piston of servomotor 29. Valve 29 is then in the neutral position to avoid application of fluid pressure to either side of the servomotor piston. As long as the contacts of thermal relay 94 remain open, the circuit of the battery 99 is interrupted and the solenoid operating means of switch 49 remains unenergized. The coil of solenoid 4I therefore remains energized and the spring I92 is retained under compression to allow free movement of the valve 29 in any direction. It will be understood that overheating of the generator will cause closing of the contacts of the thermal relay -94 which closes the circuit of the battery 99 to the switch 49 to open the switch. Spring I92 then expands to push the valve 29 toward'the right to cause closing IIDVB? ment oi the prime mover generating valve as will be described The electric current flowing in the line- 2I drives synchronous motor 12 which rotates balls9I and92tocauseshiftingofthesleeve 99sndpulltioningof thecontactarmfldependlength of the crank I91. Contacts 99 and 99 are reciprocated at a rate of speed determined wholly by the ratio of the worm and worm wheel I99 and I99. Crank I91 is however, so adjusted that, at normal frequency, contact 99 remains just out of contact with the contacts 99 and 99 at the ends of their respective strokes. Even though the auxiliary contacts of the circuit breaker 24 and the manually operable switch 64 are closed to complete energization of line 91, the circuits of relays 9i and 92 remain open, and motors 92 and 91 remain unenergized and valves 29 and 29 remain in the neutral position shown retaining the gates of the prime movers in the then attained position. Manually operable switches 99 and 91 control the maximum and minimum load limiting motors 9| and 92 and are not closed and valve 29 is therefore not influenced by any movement of such motors.

If a small speed change takes place, such as a speed increase, motor 12 operates at a higher speed, the weights 9i and 92 move farther away from the spindle 19 and the contact arm 99 is moved over fulcrum 9| in a clockwise direction. Such movement causes. contacts 99 and 99 to engage at the left hand end of the stroke of thepressure flow, to a predetermined rate, to the right hand side oi servomo'tor 29 to cause movement of the prime mover gate in the closing direction at a rate determined by the curvature of the cam face. Such movement of the gate and of the piston of servomotor 29 moves the floating lever I 42 and relays such movement to the valve 29 to restore the valve to its neutral position. If the degree of closing of the prime mover gate orvalve, in response to the actions above described, has been sufficient to reduce the speed and hence the frequency to the desired value, the. speed of the motor 12 decreases. thereby decreasing the distance at which flyballs 9I and 92 are rotated away from the spindle 19 and moving the contact arm 99 in a counterclockwise direction to the position previously occupied thereby. Contacts 99 and 99 are then out of engagement and the circuit to the coil of the relay 9I is interrupted whereupon the relay opens the circuit to the motor 92. Valve 29 being new in the neutral position, the position of the servomotor 29 is fixed at the point then attained until a further speed change occurs.

If the speed continues to increase, the above cycle of operations is repeated at an increasing rate dependent on the amount of frequency changeinthesystemwhichamountofchange controls the duration of contacting engagement oi'thecontacts99 and99. Buchcontactingmay become a continuous out which will then causemotor92tocontlnuetorotate,thuscontlnuingtomovelever I42totherightwhlchtends pleted thereto is such as left thereby rocking lever gages 'lever and the valve. 28

slipping of the clutch I'll and the motor thus merely holds the valve 28 in its extreme right hand position. Continuous rotation of the motor 32 as a result of continuing increase of speed causes continuous rotation of sleeve I5I which continues to move rod I48 to the right. Such movement of the rod is, however, limited by the position of the limiting collar I11 on such rod, which can move only until the collar I11 comes in contact with the end cap I51. The position of end cap I51 thus limits the degree to which the prime mover generating gate or valve may close and thus limits the minimum load under which the prime mover generating unit may operate, to a predetermined value. Such value is set by movement of switch 51 to cause motor 35 to rotate which rotates sleeve I53 to cause movement of the end cap I51 axially of the rod I48 either toward or away from the end of the sleeve I5I which is stationary. The sleeve I53 may be rotated in either direction merely by changing the position of switch 51 and, once the desired position is reached, sleeve I53 is allowed to remain in its then attained position by interruption of the circuit to the motor 35 by movement of switch 51 into its neutralpositlon.

If a gradual speed decrease from the predetermined value should take place, the cycle of governing operations would be similar'to those above described but would be opposite in sense and would require the use of the maximum load limit device. For momentary speed decreases, the speed of the motor 12 then decreasing, flyballs 8I and 82 contract to rock the contact arm' 89 toward the contact 98 which momentarily enwith the contact 96. A circuit is thus momentarily completed to the coil of the relay 62 which lifts the relay to complete the circuit to the motors 32 and 31. Again considering only operation of the motor 32, the circuit now comwill cause the motor to the rod I48 toward the I42 in a counterclockwise direction to move the valve 28 to the left. Such movement of the valve admits fluid pressure to; the left hand face of the piston of servomotor 26 which moves the prime mover control valve in the opening directio The relaying of the movement of the servomotor piston and the limiting of the rate of restoration of the valve 26 now takes place in a similar manner to that described above, but in the opposite sense and such description need not therefore be repeated. If the degree of gate operation which has taken place has been. sufficient to raise the speed to its predetermined normal value, the master controller contact lever 89 is returned to its previous position out of range of the stroke of contact 98 and no further action takes place. However, if the speed decrease is large and continuous, contacts 96 and 98 are continuously engaged and motor 32 continues to move lever I42 to the left to keep the valve 28 in the left hand position which continues to supply fluid pressure to the left side of the piston of servomotor 26 to move the prime mover unit gate in the opening direction. Such continuous movement of the lever I42 to the left cancels the relaying action of the remains in its extreme left hand position as determined by contact of the right hand face of cam I38 with loop I33. Continued rotation of the motor 32, continues movement of the rod- I48 to the left until the collar I16 engages the end cap I56 whereupon clutch I1I slips to avoid stalling of the motor '32. As

rotate sleeve I5I to move position, that soon as movement of the rod I48 toward the left has been stopped by the end cap I56, continued be put on the prime mover generating unit I6,

I8. The position of the end cap I56 may, of course, be varied in a manner similar to that described for the positioning of end cap I51 and which description need not therefore be repeated.

If the frequency of line 2I and hence the speed of the prime cover generating unit should change by a large amount, the cycles of action above described would be repeated dependent only on the amount of such speed change and hence on the duration of contactingengagement of contact 96 with contact 98 or 99. Such duration would be continuous as soon as contact arm 85 is moved in either direction more than one-half of the stroke of the contact yoke I63.

If it is desired to interrupt operation of the units controlled by the same master controller, it is necessary to turn hand wheel 93 in a direction to rock the contact arm 89 to bring contact 96 continuously into engagement with contact 99 which causes motor 32 to move lever I42 to the right, thereby causing valve 28 to move towards the right to admit fluid pressure on the right hand face of the piston of servomotor 26. Motor 31 then causes a similar movement of the piston of servomotor 21 and both servomotors 26 and 21 continue such movement while switches 51 and 59 are closed to the position to cause motors 33 and 38 respectively to move the minimum load limiting end cap I51 and the end cap controlled by movement of the motor 38 respectively in such direction as to permit the motors 32 and 31 to keep the valves 28 and 29 in the extreme right hand position to retain servomotors 26 and 21 moving into the gate closing position. When such gates are about closed, circuit breaker 24 will be opened to disconnect the prime mover generating unit from the transmission line 2I. Circuit breakers 22 and 23 are then opened and the portion of the system shown is entirely at rest. After the system is at rest, control arm 89 and the minimum load limiting device should again be returned to their previous position to place the system in readiness for starting and for connection with the transmission line 2|.

When it is desired to start the system, assuming that the gates of the several prime mover generating units are closed, that the servomotors 26 and 21 are in their extreme left hand position, that the valves 28-and 29 are in their neutral contact arm 89 is in the predeter: mined position for the frequency desired, that circuit breaker 24 is opened and that motor 12 is not operating, switches 63 and 64 are in the position shown and switch 66 is open thus interrupting any circuit to relays BI and 62 from the master controller. Switches 63 and 84 are then shifted to connect motors 32 and 31 to the auxiliary line 61 in a direction to move valves 28 and 29 toward the left to admit fluid pressure to the servomotors 26 and 21 to move the pistons thereof toward the right and thus to open the gates of the several prime mover generating units. The units thus come up to speed and are connected with the transmission line 2I when the output of such units is in synchronism with the line. Such synchronizing means are well known to the art and are therefore not described herein. As soon as the units are connected to the line, switches 63 and 64 are returned to the positions shown and switch 88 is closed. The minimum limiting devices having been previously moved to their previous setting and the master controller now being in operation, regulatlng operation of the unit takes place as previously described.

It will be apparent to those skilled in the art that the several units may be individually started by use of the switches 63 and 64, regardless of operation of the master controller. Any one of the units may likewise be individually stopped by movement of switches 93 and 64 out of the position shown, thus interrupting the circuit to the motors 32 and 91, which are controlled by the relays ii and 62.

The manner of operation of the master controller is illustrated in a diagrammatic way in Fig. 9, in which a diameter A, B of the circle designates the total stroke of the yoke I 03 and of the reciprocating contacts 99 and 99 and the periodic movement of such contacts is substantially illustrated by the sine curve C, D, E. Such curve is drawn with respect to an axis B, D of time abscissas, the ordinates of the points of the curve C, D, E representing the distance between contact 98, for example, and the end of the stroke thereof nearest to contact 96. The intersection of the branches C, D and D, E of the curve C, D, E with any straight line parallel to the axis B, D then defines segments such as c of the length F, G, the length of such segments representing the length of time that contact 98 remains distant from the predetermined setting of contact 96 by less than the value of the ordinate D, c of the segment. Thus, if contact 99 departs from the predetermined setting thereof by an amount equal to the ordinate D. c of segment e, such contact 96 and contact 99 will remain in engagement during a length of time F, G. During such engagement, the contacts 96 and 98 are stationary while the yoke I03 continues to follow the curve C, D, E with the effect only of causing variable compression of the spring "I. When the speed of the motor 12 is the speed desired therefore as determined by adjustment oi the wheel 93, contact 98 is in the predetermined position thereof represented by the ordinate of the line titled "normal speed" in'Flg. 9. Contact 96 then does not engage with either the contact 99 or the contact 99 during any rotation of the crank I01. When the speed of the prime mover units I6, II and I1, I! changes from the predetermined value, the flyball weights II and I2 displace contact 96 from its previous position by an amount dependent on the speed change of spindle 13. Such displacement of contact 99 causes contacts 98 or 99 to come into engagement therewith, depending on the sense of the speed change which has occurred, during each revolution of the crank ill for a predetermined length of time depending on the amount of displacement of the contact I! which varies from zero when the contact 96 reaches a position represented by the ordinate oi the axis B, D to continuous engagement when the contact 9 reaches the position represented by the ordinate D, a.

The curves shown in Fig. 10 illustrate the operation of the maximum and minimum load limit devices. Curve H is a curve plotted on ordinates of percentage of emciency of, for example, the

prime mover unit ii, I! and on abscissas oi the stroke of the servomotor 26 in tenths'to illustrate the limit of gate opening to secure operation of the unit within its most eillcient range and curve I is plotted on ordinates of horsepower output in tenths of a horsepower and on abscissas of stroke of the servomotor to illustrate the possible variations of the load within the range of control permitted by a predetermined setting of the maximum and minimum load hunting devices. It will be seen that, for an efliciency range of plus or minus 2%%, the output may be varied from .71 to .98 of full horsepower to allow the unit to take up or reject such load changes within the set range of the load limiting devices, or to assume any intermediate gate position due to the absence of any direct relaying connection between the several units and the positions provide variations in the outputs of the individual units which do not, however, disturb operation of the system because such variations are only a relatively small portion of the total output of the system. It will therefore of course be understood that the control range may be increased by proper setting of the load limit as desired to include a wider ef-- flciency range and that the amount of load regulation possible by such unit will then be correspondingly increased.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A governor for an electrically controllable prime mover comprising means driven at high speed and operating responsive to changes of speed in the prime mover, flyballs mounted to be driven by said speed responsive means, a contact member adjustably mounted and movable upon variation of the movement oi said flyballs, and contacts mounted for reciprocation adjacent said contact member and engaging therewith for periods of time varying dependent on the amount of change in the speed of said prime mover.

2. A governor for an electrically controllable prime mover comprising means operating responsive to changes in the speed of the prime movers, iiyballs driven by said speed responsive means, a contact member movable by said flyballs upon variation in the speed of movement thereof, means for adjusting the position of said contact member, contacts mounted for reciprocation intoand out of engagement with said contact member, and adjustable means driven by said sp'eed responsive means to cause reciprocation of said contacts.

3. In a system for controlling a plurality of prime movers, a power output line, a plurality of electric generators severally driven by said prime movers and connected with said line for parallel operation, means severally controlling the supply oi energy to said prime movers, means directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the operation of all of said energy supply control means, and means for limiting the range of movement of said energy supply control means, said electrical quantity responsive means controlling the operation 'of said energy supply control means and of said range limiting means.

4. In a system for controlling a' plurality of 65 electric generators severally driven by said prime prime movers, a power output line, a plurality of electric generators severally driven by said prime movers and connected with said line for parallel operation, mechanical means severally controlling the supply of energy to said prime movers, electrical means severally controlling the operation of said energy supply control means, means directly responsive to an electrical quantity to be regulated to a predetermined value in said line and actuating a plurality of contacts, and electrical means for limiting the range or movement of said mechanical means, the contacts actuated by said electrical quantity responsive means controlling the energization of all of said electrical means.

5. In a system for controlling a plurality of prime movers, a power output line, a plurality, of electric generators severally driven by said prime movers and connected with said line for parallel operation, means severally controlling the supply of energy to said prime movers, a plurality of electric motors controlling the operation of said energy supply control means, a plurality of electric motors for severally limiting the range of movement of said control motors, and means directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the operation of all of said electric motors. v

6. In a system for controlling a plurality of prime movers, a power output line, a plurality of electric generators severally driven by said prime movers and connected with said line for parallel operation, means severally controlling the supply of energy to said prime movers, a plurality of electric motors controlling the operation of said energy supply control means, a plurality of electric motors for severally limiting the range of movement of said control motors, a plurality of relays controlling the energization of all of said motors, and a single means directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the energization of all of said relays.

7. In a system for controlling a plurality of prime movers, a power output line, a plurality of electric generators severally driven by said prime movers and connected with said line for parallel operation, ply of energy to said prime movers, a plurality of electric motors controlling the operation of said energy supply control means, a plurality of elec tric motors for severally limiting the range of movement of said control means, a plurality of relays controlling the energization of all of said motors, a single means responsive directly to an electrical quantity to be regulated to a predetermined value in said line for controlling the energization of said relays, and a plurality of manually operable switches severally connected in the circuits of said motors and operable to supersede actuation of said motors by said electrical quantity responsive means.

8. In a system for controlling a plurality of prime movers, a power output line, a plurality of movers and connected with said line for parallel operation, means severally controlling the supply of energy to said prime movers, a plurality of electric motors controlling the operation of said energy supply control means, a plurality of electric motors for severally limiting the range of movement of said control motors, means severally operable by said range limiting motors for severally indicating the positions thereof, and

means severally controlling the supmeans directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the energization of all of said motors.

9. In a system for controlling a plurality of prime movers, a power output line, a plurality of electric generators severally driven by said prime movers and connected with said line for parallel operation, means severally controlling the supply of energy to said prime movers, a plurality of electric motors controlling the operation of said energy supply control means, a plurality of electric motors for severally limiting the range of movement of said control motors, variable resistances individually adjusted by operation of said range limiting motors, indicating instruments severally connected with said resistances and measuring the quantity of resistance in circuit to indicate the several positions of said range limiting motors, and means directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the energization of all of said motors.

10. In a system for controlling a plurality of prime movers, a power output line, a plurality of electric generators severally driven by said prime movers and connected with said line for parallel operation, means severally controlling the supply of energy to said prime movers, means directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the operation of all of said energy supply control means, and means severally responsive to an abnormal condition of said electric generators to supersede operation of said electrical quantity responsive means and to cause individual movement of said energy supply control means in a direction to shut off the energy supply to the several said prime movers driving said electric generator attaining predetermined abnormal conditions.

11. In a system for controlling a plurality of prime movers, a power output line, a' plurality of electric generators severally driven by said prime movers and connected with said line for parallel operations, means severally controlling the supply of energy to said prime movers, means directly responsive to an electrical quantity to be regulated to a predetermined value in said line for controlling the operation of all of said energy supply. control means, thermal relays located on and responsive to the individual temperatures of said electric generators, and means severally controlled by said relays to supersede operation of said electrical quantity responsive means and to shut off the supply of energy individually to the several said prime movers upon attainment of predetermined temperatures by' said electric generators driven thereby.

12. A governor for an electrically controllable prime mover and comprising means driven by the prime mover and responsive to the changes of speed thereof, fiyballs driven by said speed responsive said flyballs for movement thereby upon variation in the speed of operation thereof, an adjustable fulcrum for said lever, and a plurality of contacts reciprocated by said speed responsive means into and out of engagement with said contact lever.

13. A governor for an electrically controllable prime mover and comprising means driven by the prime mover and responsive to the changes of speed thereof, fiyballs driven by said speed responsive means, a contact lever connected with said'flyballs for movement thereby upon variation in the speed of operation thereof, a plurality 01 contacts reciprocated by said speed responsive means into and out of contact with said contact lever, a pointer connected with said flyballs, and a scale cooperating with said pointer to indicate the amount and the direction of any speed change.

14. A governor for an electrically controllable prime mover and comprising means driven by the prime mover and responsive to the changes of speed thereof, flyballs driven by said speed responsive means, a contact lever connected with said flyballs for movement thereby upon varia tion in the speed of operation thereof, an ad justable fulcrum for said lever, a plurality of contacts reciprocable by said speed responsive means into and out oi contact-with said-lever, a pointer connected with said i'ulcrum, and a scale cooperating with said pointer to indicate any deviation from the predetermined seating of said contact lever.

15. In a system for controlling the supply of energy to a prime mover, a fluid pressure actuated servomotor controlling the supply of energy to the prime mover, a reciprocable valve controlling the applioation of fluid pressure to said servomotor, a plurality of rotary motors mounted adjacent said valve, said motors being operable from a remote location, and means connecting said valve with one of said motors for converting the rotary motion of said motors into reciprocating motion to operate said valve and connecting said valve with the others of said motors for limiting the reciprocating motion of said valve.

16. In a system for controlling the supply of energy to a prime mover, a fluid pressure actuated servomotor controlling the supply of energy to the prime mover, a reciprocable valve controlling the application 01 fluid pressure to said servomotor, a plurality of rotary motors mounted adjacent said valve, said motors being operable from a remote location, a screw threaded rod driven by one of said motors and connected with and causing reciprocation 01' said valve upon rotation of said rod, and a plurality of stop members driven by others of said motors to limit the range of movement of said rod.

17. In a system for controlling the supply of energy to a prime mover, a fluid pressure actuated servomotor controlling the supply of energy to the prime mover, a reciprocable valve'controlling the application of fluid prmsure to said servomotor, a plurality of rotary motors mounted adjacent said valve, said motors being operable from a remote location, a threaded sleeve mounted for rotation by one of said motors, a threaded rod extending through said sleeve in engagement therewith and connected with said valve to cause reciprocation thereof upon rotation of said rod, a plurality of threaded sleeves mounted on the first said sleeve and severally driven by others of said motors, and a plurality of end caps severally mounted on and in threaded engagement with the second said sleeve to engage the ends of said rod for limiting the range of movement thereof.

ARNOLD PFAU. 

